Table 2. Amino acid composition of citrus, apple, and grape peel powders (unit: mg/100 g)

Amino acids	Citrus	Apple	Grape	F-value
Aspartic	1,099.57±32.411)a2)	894.87±21.40b	833.77±16.06c	1,597.11***3)
Threonine	231.03±5.17b	82.80±1.66c	393.93±8.35a	3,635.77***
Serine	318.13±7.19b	105.57±2.25c	470.37±5.96a	5,795.46***
Glutamic	631.47±15.85b	359.83±11.37c	1,741.07±41.60a	3,208.21***
Proline	551.13±15.33b	385.97±7.74c	459.60±13.13a	1,508.23***
Glycine	297.00±6.20b	107.20±2.65c	696.43±18.48a	2,914.89***
Alanine	333.17±8.85b	102.70±2.85c	474.10±10.50a	2,833.15***
Cystine	36.00±0.78b	19.47±0.40c	83.37±2.10a	2,935.43***
Valine	288.23±6.01b	105.23±2.48c	509.63±16.09a	1,992.38***
Methionine	43.93±1.42b	24.33±0.55c	100.77±2.30a	2,912.16***
Isoleucine	230.40±4.88b	84.90±2.08c	423.13±12.79a	2,149.76***
Leucine	398.23±9.81b	133.77±2.63c	676.43±17.39a	2,651.23***
Tyrosine	188.43±4.28b	36.27±1.00c	236.37±4.92a	3,630.57***
Phenylalanine	275.37±5.43b	79.97±1.80c	425.47±11.91a	2,539.23***
Histidine	197.60±4.52b	34.50±0.98c	305.47±7.46a	3,178.98***
Lysine	306.27±8.14b	91.80±2.08c	432.53±13.65a	1,819.00***
Arginine	275.57±5.98b	94.60±2.25c	548.60±11.78a	3,893.58***
Total4)	5,701.53±135.12b	2,743.77±83.44c	8,811.03±199.19a	2,664.17***

All values are mean±SD (n=3).
Means within a row with different superscript letters (^a-c) are significantly different (p<0.05) according to Duncan’s multiple range test.
^***p<0.001
Total amino acid content is calculated as the sum of all quantified amino acids (mg/100 g sample).